The baby of Shamima Begum, a British-born teenager who fled London to join the IS, has died in Syria.
The death has been confirmed by the US-backed Syrian Democratic Forces, who declined to specify how or when it happened.
According to the medical certificates obtained by the BBC, the three-week-old boy died of pneumonia.
Shamima, who was stripped of her UK citizenship despite her wish to return, had previously lost two other children, apparently from illness and malnutrition.